Farmers' initiatives in land husbandry: promising ... - Prolinnova

Technical Report No. 27
TECHNICAL DESCRIPTION
Categorization, purpose and impact: WOCAT system
This technology is categorized under WOCAT as a combined structural/ vegetative measure. Bunds and
channels are stabilized with perennial grass. Its purpose is primarily to increase soil moisture for crop
production, and it achieves impact through water harvesting. In soil conservation terms it reduces land
degradation and soil erosion by water.
Musyoka in his farm
Technical details
Runoff is led to the farm from the tar road in a main excavated channel of about 300 metres length,
which cuts through a neighbour’s farm. There are also supplementary channels which lead runoff from
a hillside. The estimated catchment area is (at least)10 hectares in size. This supplies water to a cultivated
area of about 5 ha. The main channel leads runoff into the farm through an initial fanya chini structure (a
channel with the earth thrown downslope). When the runoff reaches the end of the channel it is diverted
round into a similar structure, which leads the water in the opposite direction. To make a simplification,
runoff water is conveyed in a zigzag fashion, or ‘reticulated’, through the farm. At certain points the
farmer has put water control gates in specific channels, to select the direction of the flow.
The structures that transport the water within field are mainly fanya chini but some are fanya juu (embankment
above the channel). In all cases the embankment is made of earth, excavated from the channel. The
channel’s dimensions are (approx) 1.0 m deep and 1.0 – 2.0 m wide; with embankments that are 1.5 m
high and spaced at 18 m apart. These dimensions are well above those recommended for standard fanya
juu/ fanya chini design (Thomas, 1997). The structures are on a slight grade (sited by eye) to allow the water
to flow. The average field slope is 3°. The approximate vertical interval between structures is thus 0.9 m.
The embankments are stabilized with grass or perennial crops such banana or sugar cane.
Operation and maintenance
Maintenance involves frequent sediment removal to maintain channel capacity, repair of broken channels
and embankment sections and replanting grass or dried-up fruit trees along the embankment where
necessary.
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